Rate limiting with express-rate-limit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the express-rate-limit package.

Express

const rateLimit = require('[1]');

Drag options to blanks, or click blank then click option'

Aexpress-rate-limit

Bexpress

Crate-limit

Dexpress-rate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'express-rate-limit'.

Using incomplete or incorrect package names.

The package name to import for rate limiting in Express is express-rate-limit.

2fill in blank

medium

Complete the code to create a rate limiter that allows 100 requests per 15 minutes.

Express

const limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: [1] });

Drag options to blanks, or click blank then click option'

A100

B200

C50

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number too low or too high than 100.

Confusing the time window with max requests.

The max option sets the maximum number of requests allowed. Here, it should be 100.

3fill in blank

hard

Fix the error in applying the rate limiter middleware to all routes.

Express

app.use([1]);

Drag options to blanks, or click blank then click option'

Alimiter()

BrateLimit()

CrateLimiter

Dlimiter

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the limiter as a function instead of passing it.

Using undefined variables.

The rate limiter is a middleware function stored in limiter. It should be passed directly without calling it.

4fill in blank

hard

Fill both blanks to create a rate limiter that sends a custom message when limit is exceeded.

Express

const limiter = rateLimit({ windowMs: 10 * 60 * 1000, max: 50, [1]: (req, res) => { res.status(429).send([2]); } });

Drag options to blanks, or click blank then click option'

Ahandler

B'Too many requests, please try again later.'

Cmessage

D'Request limit reached.'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'message' instead of 'handler' for the function.

Passing the message as an option instead of inside the handler.

The handler option defines a function to run when the limit is exceeded. The message is sent as a string in the response.

5fill in blank

hard

Fill all three blanks to create a rate limiter with a 5-minute window, max 20 requests, and a custom message.

Express

const limiter = rateLimit({ windowMs: [1] * 60 * 1000, max: [2], handler: (req, res) => { res.status(429).send([3]); } });

Drag options to blanks, or click blank then click option'

A5

B20

C'You have exceeded the request limit, please wait.'

D'Limit exceeded, try again later.'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up windowMs and max values.

Using incorrect message strings.

The windowMs is set to 5 minutes (5 * 60 * 1000 ms), max requests is 20, and the handler sends a custom message string.

Practice

1. What is the main purpose of using express-rate-limit in an Express app?

easy

A. To handle database connections efficiently

B. To speed up the server response time

C. To automatically restart the server on code changes

D. To limit the number of requests a user can make in a time window

Solution

1. Step 1: Understand the purpose of rate limiting

   Rate limiting is used to protect the server by restricting how many requests a user can send in a short time.

2. Step 2: Identify what express-rate-limit does

   This package helps set these limits easily in Express apps.

3. Final Answer:

   To limit the number of requests a user can make in a time window -> Option D

4. Quick Check:

   Rate limiting = limit requests [OK]

Hint: Rate limiting controls request count per time window [OK]

Common Mistakes:

• Thinking it speeds up server responses
• Confusing it with server restart tools
• Assuming it manages database connections

2. Which of the following is the correct way to import and use express-rate-limit in an Express app?

easy

A. const rateLimit = require('express-rate-limit'); app.use(rateLimit({ windowMs: 60000, max: 5 }));

B. const rateLimit = require('express-rate-limit'); app.use(rateLimit());

C. import rateLimit from 'express-rate-limit'; app.use(rateLimit());

D. import rateLimit from 'express-rate-limit'; app.use(rateLimit);

Solution

1. Step 1: Check import style for CommonJS

   Using require is correct for many Express apps.

2. Step 2: Verify usage of rateLimit function with options

   We must call rateLimit with an options object like { windowMs: 60000, max: 5 } to set limits.

3. Final Answer:

   const rateLimit = require('express-rate-limit'); app.use(rateLimit({ windowMs: 60000, max: 5 })); -> Option A

4. Quick Check:

   Import + call with options = B [OK]

Hint: Call rateLimit with options object, not empty or missing [OK]

Common Mistakes:

• Forgetting to call rateLimit as a function
• Using import without proper setup
• Passing rateLimit directly without options

3. Given this code snippet, what will happen if a user sends 7 requests within 1 minute?

const rateLimit = require('express-rate-limit');
const limiter = rateLimit({ windowMs: 60000, max: 5 });
app.use(limiter);

medium

A. All 7 requests will be accepted without any limit

B. Only the first 2 requests will be accepted; the rest will be blocked

C. Only the first 5 requests will be accepted; the next 2 will be blocked

D. The server will crash after 5 requests

Solution

1. Step 1: Understand the max and windowMs settings

   The limit is 5 requests per 60000 milliseconds (1 minute).

2. Step 2: Analyze the request count

   The first 5 requests are allowed; requests 6 and 7 exceed the limit and get blocked.

3. Final Answer:

   Only the first 5 requests will be accepted; the next 2 will be blocked -> Option C

4. Quick Check:

   max 5 requests = C [OK]

Hint: Requests over max in windowMs get blocked [OK]

Common Mistakes:

• Assuming all requests pass without limit
• Thinking limit resets before 1 minute
• Believing server crashes on limit

4. Identify the error in this code snippet for rate limiting:

const rateLimit = require('express-rate-limit');
const limiter = rateLimit({ max: 10 });
app.use(limiter);

medium

A. Incorrect import statement for express-rate-limit

B. Missing windowMs option to define the time window

C. Using max instead of limit option

D. Calling app.use before defining limiter

Solution

1. Step 1: Check required options for rateLimit

   The windowMs option is needed to specify the time frame for the limit.

2. Step 2: Identify missing option

   The code only sets max but does not set windowMs, so the time window is undefined.

3. Final Answer:

   Missing windowMs option to define the time window -> Option B

4. Quick Check:

   windowMs missing = A [OK]

Hint: Always set windowMs with max for rateLimit [OK]

Common Mistakes:

• Forgetting windowMs causes no time limit
• Confusing max with limit option
• Wrong import syntax

5. You want to apply rate limiting only to the login route to prevent brute force attacks. Which code snippet correctly applies express-rate-limit only to /login?

hard

A. app.use('/login', rateLimit({ windowMs: 60000, max: 5 }));

B. app.use(rateLimit({ windowMs: 60000, max: 5 })); app.use('/login');

C. app.get('/login', rateLimit({ windowMs: 60000, max: 5 }));

D. app.post(rateLimit({ windowMs: 60000, max: 5 }), '/login');

Solution

1. Step 1: Understand how to apply middleware to specific routes

   Using app.use('/login', middleware) applies the middleware only to the /login path.

2. Step 2: Check the correct syntax for rateLimit middleware

   Calling rateLimit with options returns middleware to pass to app.use.

3. Final Answer:

   app.use('/login', rateLimit({ windowMs: 60000, max: 5 })); -> Option A

4. Quick Check:

   Middleware on route = A [OK]

Hint: Use app.use with path and rateLimit middleware [OK]

Common Mistakes:

• Calling app.use without path for specific routes
• Using app.get or app.post incorrectly with middleware
• Passing middleware after route string